Stabilized mineral oil composition



Patented Mar. 312, E9

anassi BAIL @IHL CGUSIITION No lll rag. Application February 2, 1989, serial No. 254,162

Claims.

This invention is concerned with the stabilization of viscous mineral oil fractions against the harmful effects of oxidation or deterioration with use through the use of so-called anti-oxidants or oxidation-inhibitors. The invention is more specifically related to the improvement or stabilization of such mineral oil fractions by the use of novel compounds, or a novel class of compounds, which when admixed with a viscous mineral oil in minor proportions will prevent or delay undesirable changes taking place in the oil.

As is well known to those familiar with the art, substantially all the various fractions obtained from mineral oils and refined for theirvarious uses are susceptible to oxidation. The susceptibility of anoil fraction to oxidation and the manner in which oxidation manifests itself within the oil varies with the type and degree of refinement to which the oil has been subjected and with the conditions under which it is used or tested. In other words, the products formed in an oiliraction as a result of oxidation and the degree to which they are formed depends upon the extent to which the various unstable constituents or constituents which may act as oxidation catalysts have been removed by refining operations, and also upon the conditions of use.

A highly refined viscous oil, for example, which is one that has been refined by treatment with fuming sulfuric acid or other means or combinations such as A1013, solvents and acids (or with large quantities of concentrated sulfuric acid), tends to'form relatively large amounts of acidic constituents when subjected to oxidizing conditions. The presence of catalytic materials such as copper does not appear to afiect appreciably the oxidation of highly refined oils, and such oils are less prone to the formation of colored bodies or of insoluble sludge. The formation of acidic bodies, however, is highly undesirable for most applications of these oils. For example, when used as an insulating or cooling oil in electrical equipment such as transformers or capacitors an increase in acidic bodies tends to lower the dielectric strength of the oil and has other harmful effects which are undesirable. The acids are corrosive to metals, and thus reduce the useful life of the oils as lubricants or other purposes in which they come in contact with metals, and the acidic materials are also injurious in textile lubricants and in spray oils.

Moderately refined oils, normally oils that have been refined by treatment with only moderate amounts of sufuric acid, or other refining agents, tend to form relatively small amounts of acidic oxidation products as compared with high 1y refined oils, but they undergo material color depreciation and form considerable amounts of sludge. The changes taking place in these oils are appreciably accelerated by the presence of metal catalysts such as copper. Sumcient acid is generally formed to cause some reduction in the dielectric strength of these oils, but the principal objection to them is their tendency to deposit sludge which interferes with heat transfer in transformers and turbines and also causes plugging of oil feed lines in lubricating systems.

Solvent-refined oils in general, which have been prepared by treatmentwith selective solvents, such as Chlorex, phenol, furfural, etc, resemble the moderately refined acid-treated oils in that their oxidation is accelerated by the presence of metals such as copper and further in that it is attended by substantial color depreciation and sludge formation. Acid formation is usually greater than in the case of moderately acid-refined oils, but considerably less than with highly refined oils. Both sludge and acid formation lower their value for many purposes, such as electrical insulation, lubrication, etc. Also, solvent-refined oils have found extensive use as lubricants for internal combustion engines because of their high viscosity index, but under the conditions of use encountered in crankcases such oils develop constituents which are corrosive toward certain metal bearings such as the cadmium-silver bearing, etc., which are sometimes used.

It is to be understood that this classification of oils as highly refined, "moderately refined and "solvent-refined is by no means limiting and that there can exist oils whose refining and blending has been such as to make them intermediate in properties between the types set up. Thus, response to inhibitors may be said to depend entirely on the type of oxidation and end products of oxidation of an oil, whichin'turn depends largely upon thedegree of refining this oil has had. Further, the degree of refining required to produce these types of oils varies with the crude source so that any one refining procedure may produce either a highly refined oil or a moderately refined oil, depending upon the crude source. Pennsylvania type oils, for example, require much less refining to produce highly refined oils than the Coastal type of 0115.

The use of oxidation inhibitors for the purpose of stabilizing a viscous mineral oil fraction against the deleterious effects of oxidation discussed above is well known. Since the act1on of these inhibiting materials is apparently catalytic, the problem of their development is a dificult one and is evidently influenced to a large degree by the oxidizable constituents which are in the oil following a particular refining treatment. Thus a particular inhibitor or class of inhibitors may be efiective to stabilize a highly refined oil against acid formation while the same inhibitor may have no appreciable effect upon acid, color or sludge formation in a moderately refined oil and vice versa. This same inhibitor may or may not be effective in inhibiting acid, sludge and color formation in a solvent-refined oil and may or may not be effective to inhibit the corrosive action of a solvent-refined oil toward metals such as the normally corroded alloys typified by cadmium-silver bearings.

The present invention is concerned with the production of mineral oil blends which have been inhibited against the deleterious effects of oxidation by having indorporated therein a novel characterizing ingredient. More specifically our invention has as its principal object the improvement of oils falling intothe classes hereinabove identified as highly refined oils and solventrefined oils.

Our invention is predicated upon the discovery that a product obtained by the reaction of sulfur chloride with the extracts obtained as solvent tar" from the solvent-refining of petroleum will inhibit the formation of acid in a highly refined oil and will inhibit the corrosive action of a solvent-refined oil toward alloy bearings of the type normally corroded by such oils such, for example, as cadmium-silver bearings. In this connection it is of interest to note that the reaction product of elementary sulfur on solvent tar does not possess the inhibiting or antioxidant properties noted above and that the solvent tarsulfur chloride reaction products contemplated herein do not appear to have any substantial negative catalytic effect upon color and acid formation in a moderately refined oil when exposed to oxidizing conditions in the presence of copper.

The exact chemical constitution of the antioxidant products contemplated by this invention is uncertain. We know that they are not pure compounds, since the tars extracted from petroleum oils by the conventional solvents, such as Chlorex (beta-beta-dichlor diethyl ether), phenol, furfural, etc., are a mixture of hydrocarbons probably of predominantly aromatic or cyclic nature. For this reason and further for the reason that we cannot hypothecate the reaction of sulfur chloride upon such a mixture of hydrocarbons, we cannot specify our compounds by name, but we must refer to them as reaction products, the term,solvent tar having the conventional meaning used in the art and the preferred solvent tar contemplated herein being one obtained by the treatment of a Pennsylvania oil with Chlorex.

Generalizing, we have found that sulfur chloride willreact with the highly aromatic materials extracted from petroleum in the solventrefining of lubricant stock, with the evolution of hydrochloric acid'gas and the precipitation of some free sulfur. The free sulfur can be removed by extraction with aqueous sodium sulfide and the final product obtained contains both sulfur and chlorine, probably in chemical combination with the hydrocarbon of the solvent tar.

The details in a preferred procedure for preparing antioxidants of the type employed in the mineral oil blends contemplated by this invention will be best understood from the following example:

A Chlorex tar obtained in refining a Pennsylvania oil was percolated through clay to remove some of the more resinous constituents. To 150 grams of the percolated Chlorex tar dissolved in 400 cc. of petroleum ether, grams of sulfur chloride in 400 cc. of petroleum ether were slowly added with rapid stirring. No rise in temperature occurred. The petroleum ether was distilled off, using a water bath, and the mixture was left on a hot plate at about C. until no odor of HCl or SzClz remained. A considerable amount of hydrochloric acid gas was evolved during this period. When no odor of HCl gas remained, cc. of benzene were added; the mixture was heated to the boiling point and filtered. The solvent was removed from a small portion and a per cent solution of the product in oil was prepared. This proved to be corrosive to copper when exposed at 0., indicating the presence of free or very loosely bound sulfur. To the main portion of the benzene filtrate was added 100 cc. of 20 per cent sodium sulfide. The mixture was then heated on the steam bath and stirred rapidly for severalhours, after which it was poured into a separatory funnel, 100 cc. of water was added and the mixture was allowed to stand. The benzene layer was separated, filtered and the solvent removed. The resulting material was a dark red, viscous oil that contained 1.95 per cent of chlorine and 2.77 per cent of sulfur, and A; per cent solution of this product did not corrode copper when exposed at 105 C. for 24 hours.

The general procedure described above has also been followedwithout the use of the solvent (petroleum ether) to obtain a product containing 1.72 per cent chlorine and 2.73 per cent sulfur. The combined sulfur and chlorine content of the product in both cases was in the neighborhood of from 4 per cent to 5 per cent.

The effectiveness of reaction products of the general type described above as antioxidants for highly refined oils was determined by means of a modified German tar test which involves heating a gm. oil sample at a temperature of 120 C. and bubbling oxygen gas through the oil for a period of 70 hours. The amount of acidic oxidation products thus formed in the oil was determined by titrating with caustic alkali, the results being recorded in terms of neutralization number (N. N.), which is the amount of KOH (in milligrams) required to neutralize the acids formed in one gram of oil. The oil used in this test was a transformer oil stock of the "highly refined type obtained from a Coastal distillate by successive treatments with 40 lbs. per bbl. of 98 per cent sulfuric acid and lbs. per bbl. of 103 per cent Oleum, followed by neutralization, washing and clay percolation. This oil stock has a specific gravity of 0.871, a flash point of 310 F. and a S. U. viscosity of 69 seconds at 100 F.

The results of the test are given in Table I below, where oil A indicates the oil alone and oil "18" indicates the same oil containing 0.10 per cent of the reaction product of sulfur chloride and Chlorex solvent tar obtained by the procedure outlined above.

Table I Oil N. N. after test A 25.00 B o. as

To demonstrate the effectiveness of the reaction products contemplated herein as inhibitors of areaeei grams was put in 30 grams of the oil sample which was heated to 175 C. for 22 hours while a stream of air was bubbled against the surface of the bearing. The loss in weight of the bearing caused by this treatment is a measure of the amount of corrosion. The oil used in this test was a S. A. E 20 motor oil of the solvent-refined type obtained by the solvent extraction with Chlorex of a Pennsylvania mixed neutral residuum stock, such oil having a specific gravity of 0.872, a flash point of 435 F., and a S. U. viscosity of 318 seconds at 100 F. The results obtained are listed in Table II below:

From the results of the foregoing tests it will be seen that reaction products of. the type contemplated by this invention are effective to inhibit acid formation in a highly refined oil and to retard the corrosive action of solventrefined oils toward alloy bearing metals. The amount of the antioxidant used may be varied, depending upon the oil fraction and the conditions under which it is used, and in general it appears that amounts from about 0.05 per cent to about 5.0 per cent are sumcient to effect the desired results.

It is to be understood that the terms highly refined and solvent-refinedflas used herein are not necessarily confined to the identification of oils produced by a particular refining treatment but are intended as being descriptive of any oil having deteriorating characteristics and inhibitor response similar to the examples given. As has been previously pointed out, these characteristics in an oil are effected by the crude stock used as well as by the refining treatment. It is possible, for example, by proper selection of the crude to obtain a highly refined oil with a refining treatment which by the use of another crude stock would produce an oil whose inhibitor response and oxidation products would characterize it as a "moderately refined oil.

We claim:

1. An improved mineral oil composition having in admixture therewith a minor proportion of the product obtained by reacting sulfur chloride with a solvent tar derived from the solvent extraction of petroleum and treating the reaction product to remove corrosive sulfur, said reaction product being present in suficient amount to inhibit the deleterious effect of oxidation upon the oil.

2. An improved mineral oil composition comprising a mineral oil fraction selected from the group consisting of highly refined oils and solvent-refined'oils and having in admixture therewith a minor proportion of the product obtained by reacting sulfur chloride with a solvent tar derived from the solvent extraction of petroleum oil and treating the reaction product to remove corrosive sulfur, said reaction product being present in an amount sufiicient to inhibit the deleterious efiects of oxidation on the oil.

3. An improved mineral oil composition comprising a mineral oil fraction selected from the group consisting of highly refined oils and solvent-refined oils and having in admixture there-. with a minor proportion of the product obtained by reacting sulfur chloride with a solvent tar derived from the solvent extraction of petroleum oil with Chlorex and treating the reaction product to remove corrosive sulfur, said reaction product being present in an amount sumcient to inhibit the deleterious effects of oxidation on the oil.

4. An improved mineral oil composition comprising a mineral oil fraction selected from the group consisting of highly refined oils and solvent-refined oils and having in admixture therewith a minor proportion of the product obtained by reacting about 150 parts by weight of Chlorex solvent tar with about 25 parts by weight of sulfur chloride at a temperature in the neighborhood of 80 C. until evolution of HCl has substantially ceased, adding a sodium sulfide solution to the reaction mixture in sufiicient amount to remove corrosive sulfur and separating the sodium sulfide solution to obtain the solvent tar-sulfur chloride reaction product, said reaction product being present in an amount sufficient to inhibit the deleterious efiects of oxidation on the oil.

5. An improved mineral oil composition comprising a mineral oil fraction selected from the group consisting of highly refined oilsand solvent-refined oils and having in admixture therewith a minor proportion of the product obtained by reacting about 150 parts by weight of Chlorex solvent tar with about 25 parts by weight of sulfur chloride at a temperature in the neighborhood of 80 C. until evolution of HCl has substantially ceased, adding a sodium sulfide solution to the reaction mixture in sufilcient amount to remove corrosive sulfur and separating the sodium sulfide solution to obtain the solvent tarsulfur chloride reaction product, said reaction product being present in an amount ranging I from about 0.05 per cent to about 5.0 per cent sufficient to inhibit the deleterious effects of oxidation on the oil.

6. An improved mineral oil composition hav- I ing in admixture therewith a minor proportion of the reaction product obtained by treating a solvent tar obtained from the Chlorex extraction of a Pennsylvania petroleum stock with sulfur chloride and treating the reaction product to remove corrosive sulfur, the proportions of acid reactants being such that the product obtained after removal of the corrosive sulfur has a sulfur and chlorine content in the neighborhood of from 4 per cent to 5 per cent, said reaction product being present in an amount sufiicient to inhibit the deleterious efiects of oxidation on the oil.

LYLE A. HAMILTON.

EVERETT W.

March 312 14@. g w, E al gfifil HIGH FREQUENCY APPARATUS Filed April 9, 1936 3 Sheets-Sheet 1 Inverw to r": ChesterW. Dice,

by A

His ttomeg.

CER'IEICATE OF CORRECTION. Patent-No. 2,195,551. March 12, 191w.

LYLE A. HAMILTON, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, first column, line 51;, for "sufuric". read --su1furic--; page 2, second column,

line 55, for the word "has" read -had--; page 5, first column, line '21, Table II, for "2595* read "0.25 and that the said Letters'Petent should be read with this correction therein that the same may conform to the rec- 0rd of the case in the Patent Office.

Signed and sealed this 9th day of July, A. D. 1914.0.

Henry Van Arsdale,

(seal) Acting Commissioner of Patents. 

